Atomic absorption spectrophotometry using electrothermal atomization and neutron activation analysis have been used for the quantitation of platinum, vanadium, nickel, cobalt, calcium, and iron and some other elements in biological tissues and fluids. Electrochemical techniques are being developed for analysis of some elements. The analyses are important in clinical biochemical, pharmacokinetics and binding studies. The analytical techniques must be very sensitive because in most instances these elements are present in trace concentrations in the samples typically of interest e.g. part-per-million 10 to the-6g/g), part-per-billion (10 to the-9g/g), and in some cases even the part-per-trillion 10 to the-12g/g while sample volume is also often small (typically 0.5 ml or less). Various separation techniques such as chromatography, solvent extraction, and electrophoresis have been used to purify samples and fractionate and concentrate chemical species for analysis and reduce or eliminate interferences. Microprobe techniques using instruments such as the electron probe microanalyzer have also been to localize elements on the microscopic scale in sub-cellular structures in different tissues.